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UNITED STATES PATENT OFFICE 2,570,297 AMNO ACD SYNTHESIS David I

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UNITED STATES PATENT OFFICE 2,570,297 AMNO ACD SYNTHESIS David I Patented Oct. 9, 1951 2,570,297 UNITED STATES PATENT OFFICE 2,570,297 AMNO ACD SYNTHESIS David I. Weisblat and Douglas A. Lyttle, Kala mazoo, Mich., assignors to The Upjohn Com pany, Kalamazoo, Mich., a corporation of Michigan No Drawing. Application November 29, 1946, Serial No. 713,094 3 Claims. (CI. 260-534) 1. 2 The present invention relates to the prepara (1928)). Because of the difficulty of synthesis, tion of amino acids and is more particularly the preferred method of obtaining this amino concerned with a novel method for the Synthesis acid is by the hydrolysis of gelatin (Blatt Organic of alpha amino acids. Syntheses, col. vol. II, 59-62, John Wiley and The significance of the alpha amino acids in Sons, New York, 1943). Histidine has been pre human and animal nutrition makes their Syn pared by procedures 2, 3, (a) and 4 (c). Waline thesis generally of great importance. The volumi (Organic Syntheses 20, 106 (1940)), leucine, and nous literature and the great number of attempts isoleucine are best prepared by methods 1 and 3 to find suitable procedures for the preparation of (a). Phenylalanine has been prepared by meth alpha primary amino acids is indicative of this 0. ods 3 (b), 4 (b) and 4 (c). (Blatt Org. Syn., importance. (Gilman, Organic Chemistry, vol.II, col. vol. II, 489-94, John Wiley and Sons, New "Natural amino acids,' by H. T. Clark, pp. 1079 York, 1943.) Threonine has been prepared by a 1166, John Wiley and Sons, New York, 1943; procedure under method 2 (Org. Syn. 20, 101, Schmidt, “The Chemistry of Amino Acids and John Wiley and Sons, New York, 1940), the neces Proteins," chapter II, "The Constitution and syn 5 Sary halogen acid being obtained from crotonic thesis of amino acids' by Max S. Dunn, Charles acid. C. Thomas, Baltimore, 1938; Wickery and Schmidt, Other amino acids which are not considered Chem. Rev. 9, 169-318 (1931)). The principal as essential to certain animal diets have been methods which previously have been employed prepared by variations of these methods. They for the preparation of amino acids involve: i. 20 are aspartic acid, glutamic acid, hydroxyglutamic The cyanohydrin synthesis (Strecker synthesis). acid, glycine, alanine, norieucine, serine, cysteine 2. The action of ammonia on alpha halogen acids. and tyrosine. 3.Reactions using malonic esters (a) to give alpha Inasmuch as the amino acids appear to play an halogen acids for method (2), (b) reaction of increasingly important role in the nutrition and phthalamidomalonic ester with halogen Com 25 physiology of the human race, the importance pounds, (c) reactions of amino malonic esters, thereof, as well as the importance of a new and (d) reaction of potassium ethylmalonates with more practicable synthesis therefor, is considered hydrazine. 4. Condensation of aldehydes with (a) obvious. hydantoin, (b) diketOpiperazine, (c) hippuric It is an object of the present invention to acid (azlactone method). 5. From alpha, keto provide a new method for the synthesis of amino acids by (a) reduction and amination, (b) re acids. An additional object of the invention is duction of oximes, (c) reduction of hydrazones. the provision of a method for the synthesis of Detailed procedures for the production of alpha amino acids in a manner which may be conducted amino acids usually involve, in Some stage of the With increased facility in comparison with known synthesis, one of these general methods. The 35 methods. A further object of the invention is the preparation of tryptophane from gramine (Al provision of a novel method for the synthesis bertson et al., J. Am. Chem. Soc. 66, 500 (1944), of amino acids which will be more economically 67, 36-7 (1945); Snyder et al., J. Am. Chem. Soc. and commercially practicable. Another object 66, 350 (1944); Howe et al., J. Am. Chem. Soc. of the invention is the provision of a novel method 67, 38 (1945)) may be considered as a variant of 40 for the production of amino acids which in method 3 (b). The preparation of methionine volves the alkylation of an ester of nitroacetic (Windus and Marvel, J. Am. Chem. Soc. 52, 2575 acid. A further object of the invention is the (1930); Barger and Weichselbaum in Blatt Org. provision of a process for the preparation of Synthesis, col vol. II, 384, John Wiley and Sons, anino acids which includes the step of reducing New York, (1943) proceeds through malonic ester an alpha nitro acid or an ester thereof. Another or phthalimidomalonic ester by procedures 3 (a) object of the invention is the provision of a and 3 (b). Ornithine, necessary for the prepar method for the Synthesis of amino acids which ation of arginine, has been prepared by method 3 proceeds through nitro acids or nitro acid esters (b) (Fischer, Ber. 34,454 (1901)), as the dipicrate corresponding to the desired amino acid. A fur from CH2=CH-CH=CH-COOH (beta vinyla ther object of the invention is the provision of a crylic acid) and ammonia (Fischer and Raske, novel method for the synthesis of amino acids Ber. 38, 3607 (1905)), and as the dibenzoyl de which may be conducted in three steps from the rivative, by Kumatsu and Sugasawa, following starting nitroacetate, or with various combina an eleven step procedure from acrolein (J. Pharm. tions of steps when starting with an intermediate. Soc., Japan, 48, 24 (1929); Chem Abstr. 28, 1758 Another object of the invention is the provision 2,570,29? 3 4. of a method for the preparation of amino acid compounds have been found especially satisfaca which proceeds through the steps of alkylation, tory, and their employment in the alkylation reduction, hydrolysis and, if desired, resolution. step therefore constitutes a preferred embodil Another object of the invention is the provision ment of the invention. of a process which involves the alkylation of an The alkylation step of our new synthesis may, ester of nitroacetic acid, reduction and hydrolysis for example, be carried out by reacting together of the resulting nitro acid ester to the amino an ester of nitroacetic acid, e. g., ethyl nitro acid. Another object of the invention is the pro acetate, and a suitable alkylating agent, for ex vision of a process for the preparation of Optical ample, One Such as is utilised in the preparation isomers of amino acids in substantially pure 10 of tryptophane, gramine (3 - dimethylamino form. A still further object of the invention is methylindole), with or without the employment the provision cf novel compounds, intermediates Of alkali and heat. We have found that when in the preparation of amino acids, including the process is conducted in this manner, e. g., esters of nitro acids, the nitro acids themselves, with the employment of a nitroacetate and a and, in some cases, the esters of the amino acids. 5 Substituted dialkylamine such as gramine, it is Other objects of the invention will be apparent usually advantageously, although not necessarily, from the following specification and claims. carried out in an anhydrous organic solvent such . The method of our invention is generally ap as xylene, while passing a slow stream of nitro plicable to the preparation of the above-named gen through the reaction with vigorous agitation, and other primary alpha amino acids. The 20 at a temperature usually up to about 100 degrees method of our invention essentially involves the centigrade over a period of five hours, more or treatment of an ester of nitroacetic acid, e. g., less. During this period of heating, a consider ethyl nitroacetate, with a selected "alkylating able quantity of dialkylamine (dimethylamine agent," i. e., an agent of the alkylating type from gramine) is evolved. The hot solution may which is capable of introducing a desired group 25 then be filtered from a small amount of crystal into the acid portion of the nitroacetate mole line solid which usually forms and the xylene cule at the alpha carbon atom, reduction of the removed by concentration in vacuo. The residual nitro ester thus formed, isolation of the amino gun may be dissolved in chloroform, the solu ester and separation of the same into its optical tion extracted with dilute hydrochloric acid and enantiomorphs if desired, and hydrolysis of the 30 washed with water until neutral. The remain amino ester to the particular amino acid con ing solution may be dried, concentrated in a cerned. vacuum, freed of excess nitroacetate by distilla The alkylation step. of our new Synthesis may tion under reduced pressure, dissolved in chloro be carried out by reacting together any desired form. Or similar Solvent, and extracted to ex ester of nitroacetic acid, or salts thereof, and a 35 haustion with dilute alkali. After acidification Selected "alkylating agent.' By "alkylating and extraction with chloroform or similar Sol agent,' as herein employed, is intended any vent, drying and concentrating the last chloro agent comprising at least a selected group, and form extract usually leaves an oil which may capable of introducing said group into the acid be crystallised readily. This oil is an ester of portion of the nitroacetate molecule at the alpha 40 the desired substituted nitroacetic acid, in the carbon atom. As agents in this capacity may case of the foregoing example wherein gramine and ethyl nitroacetate were reacted, of alpha be mentioned: nitro-beta- (3-indole) propionic acid, in a sub 1A. Alkyl halides, alkyl arylsulfonates, and stantially pure form. Other methods may be alkyl sulfates with a basic catalysis; m employed to separate the ester and will be ap B. Carbinols with boron trifluoride catalysis; 45 parent to One skilled in the art.
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